问题 I have an app that stores some data in room database. At first, my adapter was like that: public class ViewCourseAdapter extends ListAdapter<Course, ViewCourseAdapter.ViewCourseHolder> { private int previousPosition = 0; public ViewCourseAdapter() { super(DIFF_CALLBACK); } private static final DiffUtil.ItemCallback<Course> DIFF_CALLBACK = new DiffUtil.ItemCallback<Course>() { @Override public boolean areItemsTheSame(@NonNull Course oldItem, @NonNull Course newItem) { return oldItem.getId() ==